The continued development and study of new polymer membrane based potentiometric gas and anion selective sensors is proposed. This Phase IV research program will build upon recent successes in devising very simple sensors suitable for direct biomedical and environmental monitoring applications. Efforts in the gas sensing area will focus on: 1) further improving the in vivo performance of new dual ion/gas sensing catheter devices developed during the most recent grant period; and 2) conducting feasibility studies regarding the development of a new potentiometric pO2 sensor which could ultimately be incorporated into similar in vivo catheter configurations. Actual in vivo evaluation of the dual ion/gas sensing catheters will be conducted in the Department of Anesthesiology at the University of Michigan Hospital and will be directed toward simplifying the fabrication and improving the biocompatibility of these devices. The latter efforts will focus on determining the compatibility of various non-thrombogenic polymeric materials and coatings, including covalently bound polyethylene oxides, with the membrane chemistries required for reliable potentiometric detection of the ions and pCO2. Those polymer materials and coatings that provide increased biocompatibility without interfering with the sensing chemistries will be used to fabricate the various catheter designs. Work on the new P02 sensor will involve studying the potentiometric behavior of membranes doped with various CO(II) complexes that bind oxygen reversibly at room temperature. These membranes will be deposited on the surfaces of standard inert redox electrodes, and potentiometric oxygen sensing will be achieved by monitoring the redox potential of the Co(II)/Co(III) couple within the polymeric film. Expanded investigations in the area of anion selective sensing electrode systems will center on the use of organometallic complexes, including metalloporphyrins, as ionophore type components in polymeric membranes. These studies will include: 1) examining the response mechanisms and improving the analytical performance of several new anion sensors (salicylate, thiocyanate, and sulfite) developed during the most recent support period; 2) screening a wide range of additional metalloporphyrin species to determine the effect of the metal center and its oxidation state on the observed anion binding selectivities; and 3) determining the feasibility of using electropolymerized films of metalloporphyrins and/or metallophthalocyanines as anion binding template structures to devise potentiometric sensors with unique selectivities toward biologically important anions (e.g., phosphate, chloride, etc.).